Conventionally, in order to prevent cardiovascular attacks such as syncope caused by rapid lowering of blood pressure in medical emergency fields and/or medical hemodialysis fields, blood pressure of patients is measured either in a continuous manner or in a certain constant interval. When the blood pressure is lowered, necessary medical treatments are carried out.
As methods of measuring blood pressure in these medical fields, there is such a method capable of noninvasively measuring blood pressure under noninvasive condition. As this noninvasive measuring method for blood pressure, the following measuring method has been proposed. That is, while a cuff is mounted on a major portion of body (for example, arm), Korotkoff sound caused by blood vessel is detected, which is caused by a pressure change occurring in the blood vessel, so as to estimate systolic and diastolic blood pressure values. Also, another method has been proposed in, for instance, U.S. Pat. No. 5,255,686 (JP-A-5-7558), in which cuff pressure is adjusted in response to a signal derived from a pressure sensor which detects cuff pressure. However, in these conventional methods, blood pressure cannot be monitored in a continuous manner.
It is proposed to avoid such a problem that in order to reduce loads given to a patient, when blood pressure of this patient is under stable condition, a blood pressure measuring operation is interrupted, whereas when the blood pressure is lowered (namely, only when blood pressure measurement is required), cuff pressure is applied to this patient so as to measure the changing blood pressure. However, there is no means capable of determining whether or not blood pressure of a patient is lowered without actually measuring the blood pressure. As a consequence, while cuff pressure is applied to the patient either in a continuous manner, or in an interrupt manner, the blood pressure thereof should be measured.
Also, in such a case that a patient is brought into a syncope state, since blood pressure of this patient is rapidly lowered, even when the blood pressure is monitored, an omen of this rapid-lowering blood pressure cannot be easily discovered. As a consequence, it is practically very difficult to discover such a blood pressure abnormality in an earlier stage.